robertson



(No Model.) 2 Sheets-Sheet 1.

J. H. ROBERTSON.-

CENTRAL OFFICE SYSTEM FOR AUTOGRAPHIG TELEGRAPHS.

No. 425,086. Patented Apr 8, 18-90.

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(No Model.) 2 Sheets-Sheet 2.

J. H. ROBERTSON. CENTRAL OFFICE SYSTEM FOR AUTOGRAPHIG TELEGRAPHS.

No. 425,086. Patented Apr. 8, 1890.

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UNITED STATES ATENT OFFICE.

JAMES H. ROBERTSON, OF RUTHERFORD, NEV JERSEY, ASSIGNOR TO THE \VRITINGTELEGRAPH COMPANY, OF NE\V YORK, N. Y.

CENTRAL-OFFICE SYSTEM FOR AUTOGRAPHIC TELEGRAPHS.

SPECIFICATION forming part Of Letters Patent No. 425,086, dated April 8,1890.

Application filed August 30, 1886. Serial No. 212,165. (No model.)

To all whom it may concern.-

Be it known that 1, JAMES H. ROBERTSON, a citizen of the United States,and residing in Rutherford, Bergen county, New Jersey, have invented anew and useful Improvement in Exchange or Central Office Systems asApplied to Telegraphs, especially Autographic Telegraphs, of which thefollowing is a specification.

This invention is intended to be used in connection with the autographictelegraphs for which I have heretofore filed several applications forLetters Patent, notably application Serial No. 206,692. The instrumentsof such a telegraph are of course adjusted to operate at a certainresistance of the eircuitt'. 6., they are so adjusted that they willoperate best at a particular resistance. When, however, numerousinstruments located at various points are connected with a centraloffice, it follows that there will be a great difference in theresistance of the several connectingconductors, and that in those caseswhere the resistance of the circuit differs widely from that to whichthe instruments are adjusted the latter will not work satisfactorily,'orperhaps not at all. To adjust in each such case the resistance of theinstruments would be impraticable, as it would require experiencedoperators, the employmentof which it is desired to make unnecessary. Itis therefore desirable to have some means whereby the combinedresistance of any two subscribers lines that may be connected with eachother may be made approximately the same. I accomplish this object bythe means hereinafter described and claimed.

In my application hereinbefore referred to I have shown and describedthe instruments of subscribers connected and operated by two conductors;but for the sake of clearness I have shown in all but Fig. 3 of theseveral figures of the accompanying drawings only one conductor. It is,however, possible to operate the instruments by only oneconnecting-conductor, as described in Gowpers English Patent No. 1,242of 1879, for example.

In the drawings herewith, forming part of this specification, Figure 1represents a view of an automatic means of my invention foraccomplishing the object I havein view. Fig.

2'illustrates a modification, which also operates automatically. Fig. 3represents the construction shown in Fig. 1 applied to a doubleswitchcord.

In Fig. 1 I have shown 1 six subscribers lines, 1 2 3 4t 5 6, ofvaryingresistance, entering a central office. Two switches 7 S,electrically connected with each other, are used for connecting theseveral subscribers with each other. In the conductor connecting theswitches are placed the battery 9, electromagnet 10, and a pile ofcarbon disks 11. The armature 12 of the said electro -magnet is mountedon a flat spring 13, held at both ends, as shown, and is provided with acontact-point, which bears on spring 14, placed in front of the carbondisks. I have shown two lines of two hundred and one hundred ohmsresistance connected with each other, making a combined resistance ofthree hundred ohms, disregarding resistance of battery, electromagnet,and pile of carbon disks. If lines 1 and 5 were connected with eachother, the combined resistance would be only twentytwo ohms. As all theinstruments of the several subscribers are adjusted approximately thesame, it is obvious that the battery suitable for a circuit of threehundred ohms resistance would be too strong for a circuit of onlytwenty-two ohms resistance. The mechshown and described compensates,however, for differences in'the resistance of circuits in the followingmanner:

In switching from a circuit of high resistance to one of low resistancethe strength of the current is increased, and this operates to draw downarmature 12, thus lessening the pressure on the pile of carbon disks,and consequently increasing the resistance of this part of the circuit.In this manner resistance is automatically inserted in the circuit tocompensate for what was taken out. After a bal ance is obtained thearmature is locked in place by means of screw 29 passing through 5 block28, suitably supported.

I do not desire to limit myself to any particular form of lockingmechanism, as any locking means that will accomplish the saine object iswithin the scope of my invention. Ico Neither do I desire to limitmyself to any particular means whereby the combined resistance of anytwo conductors that may be con nected with each other is madeapproximately the same when I combine this means with a lockingmechanism.

The screw pressing against the side of armature prevents its furthermovement. In Fig. 2 the screw presses the core of the solenoid againstthe side of the opening in the coil, and thus holds the core in place.The view of the locking mechanism shown in Fig. 2 is a side view of thatshown in Fig. 1.

In Fig. 2 a solenoid 15 is substituted for the electro-magnet of Fig. 1,the core of which solenoid is pivoted to a lever 16, one end of which isarranged to make connection with a series of resistance-coils 17 18 192O 21, graduated in resistance. As the strength of the current isincreased by reason of a decrease in resistance of circuits connected,the core pulls the lever down, thus introducing more and more resistanceinto the circuit the farther the lever is pulled down. The said lever isprovided with a counter-weight 22 to returnit to a normal position whenthe strength of the current is decreased.

In Fig. 3 I have shown a switch-core 28 with double line and a batteryand an automatic regulator, such as is shown in Fig. 1 in each line.

I do not herein broadly claim the combination,with a number ofconductors terminating in a central ofiice, of means whereby thecombined resistance of any two conductors that may be connected witheach other is made approximately the same, as I have laid claim to thatin application Serial No. 219,581, filed November .33, 1886, Patent No.403,291.

I am aware that it is not new to provide a single line with an automaticmeans for keep-- ing the resistance of said single line constant; butthis is not what I claim.

Having thus described my invention, what I claim, and desire to secureby Letters Patcnt, is

1. The combination, with a number of conductors terminating in a centralor exchange office and switching means for electrically connecting anytwo of said conductors, of a regulator whereby the combined resistanceof any two conductors that may be connected with each other is madeapproximately the same and a locking mechanism, substantially asdescribed.

2. The combination, with a number of conductors terminating in a centralor exchange office and switching means for electrically connecting anytwo of said conductors, of an automatic regulator whereby the combinedresistance of any two conductors that may be connected with each otheris made approximately the same, substantially as described.

8. The combination, with a number of conductors terminating in a centralor exchange oilice, of a battery, electro-magnet, and armature, and apile of carbon disks, all arranged in the conductor for connecting thecircuits, the armature being mounted to exert more or less pressure onthe pile of disks as the strength of the current decreases or increases,substantially as described.

In testimony whereof I have hereunto subscribed my name.

' JAMES II. ROIBER'ISON.

\Vitnesses:

L. A. GIEGERICH, Gno. II. GRAHAM.

